Java is a robust, object-oriented programming language expressly designed for use in the distributed environment of the Internet. Java can be used to create complete applications that may run on a single computer or be distributed among servers and clients in a network. A source program in Java is compiled into byte code, which can be run anywhere in a network on a server or client that has a Java virtual machine (JVM).
A JVM describes software that is nothing more than an interface between the compiled byte code and the microprocessor or hardware platform that actually performs the program's instructions. Thus, the JVM makes it possible for Java application programs to be built that can run on any platform without having to be rewritten or recompiled by the programmer for each separate platform.
Jini is a distributed system based on the idea of federating groups of users and the resources required by those users. Resources can be implemented either as hardware devices, software programs, or a combination of the two. The Jini system extends the Java application environment from a single virtual machine to a network of machines. The Java application environment provides a good computing platform for distributed computing because both code and data can move from machine to machine. The Jini infrastructure provides mechanisms for devices, services, and users to join and detach from a network. Jini systems are more dynamic than is currently possible in networked groups where configuring a network is a centralized function done by hand.
However, the Java/Jini approach is not without its disadvantages. Both Java and Jini are free, open source applications. The Java application environment is not designed for controlling messaging between different machines. For example, the Java application is not concerned about the protocols between different hardware platforms. Jini has some built-in security that allows code to be downloaded and run from different machines in confidence. However, this limited security is insufficient for environments where it is necessary to further restrict code sharing or operation sharing among selected devices in a secure embedded system.